( 508 ) 
So in all 16 pieces. From this list appears that at an early time 
already these boulders have attracted the attention. Quite in corre- 
spondence with this is the fact that as early as 1878 Martin men- 
tioned 11 pieces from Groningen (6, p. 21, a and c), and even 
earlier still Rozmrr observed such boulders from here (1, p. 387, 
n°. 16; 3, p. 269, n°. 27). Afterwards van CALKER also pointed out 
their occurrence in the Hondsrug (19, p. 357; 25, p. 363). 
As regards the further spreading of this species of boulders, I refer 
to Rormer’s excellent treatise about everything known at the time 
about this subject (18, p. 75), and only wish to state here, that in 
Germany these boulders are found in a great many places, but nowhere 
in large quantities. So everywhere in East- and West-Prussia (20, 
p. 58), in Posen, Silesia and Brandenburg, near Sorau in the district 
of Frankfurt on the Oder, in South-Holstein in various localities 
(18, p. 45). Further north they seem not to occur, more westward, 
on the other hand, Lüneburg in Hannover and Jever in Oldenburg 
are still to be called as places where they are found. Afterwards 
WaAHNscHAFFE has made mention of a specimen found near Havelberg 
(14), and various observations attached to it as to the value of these 
boulders for the determination of the direction of the ice-flow and the age 
of the diluvial deposits, in which they are found. [ hope afterwards 
to recur to this question. In Pomerania the Borealis-limestone is not 
(vet) known (31, p. 83), no more, it seems, in Mecklenburg. SToLLEY 
afterwards states that he has found it again in Sleswick-Holstein, 
but differs in this respect from all other notations known to me that 
he has come upon greater numbers of dolomites than of limestones 
(30, p. 98). Lastly, these boulders are neither rare in the regions 
south of the Russian Baltie provinces. 
While, as we see, an enormous tract is taken up by the erratics, 
the Borealis-limestone occupies but a very small part as solid rock. 
In the eastern baltie (8, p. 48) it forms Scumipr’s zone G,, the 
Borealisbank, which stretches in E.-W.-direction throughout Esthonia, 
in the shape of a zone narrowing to the west, which also appears 
in the island of Dagö. The rock consists of limestone or dolomite, 
just like the boulders, and for a long time only single valves of 
Pentamerus borealis Ercnw. have been found in it. Afterwards ScumiptT 
has discovered also complete specimens of this species, in a marly 
variety of the rock from the neighbourhood of Hapsal, as already 
stated (27, p. 130). 
Of this eastern-baltie occurrence I possess limestones for comparison 
from Risti in the extreme west of this zone on the mainland and 
dolomite from Pantifer in East-Esthonia, Our boulders correspond 
